The present invention is directed to ink compositions and more specifically, the present invention relates to semi-solid hot melt inks with a melting point of for example, from about 25.degree. C. to about 40.degree. C., and which inks are especially useful for acoustic ink printing, processes and apparatuses, reference, for example, U.S. Pat. No. 5,121,141, U.S. Pat. No. 5,111,220, U.S. Pat. No. 5,128,726, U.S. Pat. No. 5,371,531, the disclosures of which are totally incorporated herein by reference, including especially acoustic ink processes as illustrated in the aforementioned copending applications such as an acoustic ink printer for printing images on a record medium.
The inks of the present invention in embodiments thereof are comprised of (1) a liquid non-aqueous vehicle with a boiling point of higher than, or equal to about 150.degree. C. and lower than, or equal to about 350.degree. C., and more specifically from about 175 to about 325, and yet more specifically from about 225 to about 300 degrees Centigrade, and low acoustic loss to reduce, or minimize energy consumption, and which acoustic loss is for example, below, or about equal to 60 dB/mm, (2) a solid paper ester contained in the pores of a substrate, such as paper and which ester possesses a melting point of for example, lower than about, or equal to about 75.degree. C. and preferably between about 35.degree. to about 74.degree. C. and with a low acoustic loss of from about less than about 100 dB/mm, (3) a liquid crystalline ester compound, (4) a lightfastness UV absorber, (5) a lightfastness antioxidant, (6) and a colorant such as a dye, a pigment or mixtures thereof. More specifically, the present invention is directed to semi-solid hot melt acoustic ink compositions comprised of (1) non-aqueous ester liquid vehicles with a boiling point of for example, higher than about 150.degree. C. and lower than about 350.degree. C., preferably between about 170.degree. and about 300.degree. C., and with a low acoustic loss below or equal to about 60 dB/mm, and preferably in the range of between about 5 to about 40 dB/mm, (2) a non-aqueous solid ester with a melting point of for example, lower than about 75.degree. C. and preferably between about 35.degree. to about 74.degree. C., and with a low acoustic loss below, or equal to about 100 dB/mm, and preferably in the range of between about 25 to about 80 dB/mm, (3) a liquid crystalline ester compound, (4) an ester UV absorber, (5) an ester antioxidant, and (6) a colorant, and wherein there can be generated with such inks excellent developed images on substrates, such as plain and coated papers with acceptable image permanence, excellent projection efficiency on transparencies without a post fusing step, and excellent crease resistance, and wherein the inks possess acceptable, and in embodiments superior lightfastness, and superior waterfastness. Moreover, in embodiments of the present invention there is enabled the elimination, or minimization of undesirable paper curl since water is preferably not present in the inks, and it is preferred that there be an absence of water, thus a dryer can be avoided thereby minimizing the cost of the acoustic ink jet apparatus and process.